EHCI: force high-speed devices to run at full speed

This patch (as710) adds a sysfs class-device attribute file named
"companion" for EHCI controllers.  The file contains a list of port
numbers that are dedicated to the companion controller; by writing a
port number to the file the user can force a high-speed device
attached directly to the computer to run at full speed.  (As far as I
know it is not possible to do this for a device attached to an
external hub.)  A port is removed from the file by writing the
negative of its port number.

Several users have asked for this facility and it seems like a useful
thing to have.  Every now and then one runs across a device which
behaves much better at full speed than at high speed.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-hcd.c

@@ -388,6 +388,7 @@ static void ehci_stop (struct usb_hcd *hcd)
 	/* let companion controllers work when we aren't */
 	ehci_writel(ehci, 0, &ehci->regs->configured_flag);
 
+	remove_companion_file(ehci);
 	remove_debug_files (ehci);
 
 	/* root hub is shut down separately (first, when possible) */
@@ -563,6 +564,7 @@ static int ehci_run (struct usb_hcd *hcd)
 	 * since the class device isn't created that early.
 	 */
 	create_debug_files(ehci);
+	create_companion_file(ehci);
 
 	return 0;
 }

drivers/usb/host/ehci-hub.c

@@ -188,6 +188,103 @@ static int ehci_bus_resume (struct usb_hcd *hcd)
 
 #endif	/* CONFIG_PM */
 
+/*-------------------------------------------------------------------------*/
+
+/* Display the ports dedicated to the companion controller */
+static ssize_t show_companion(struct class_device *class_dev, char *buf)
+{
+	struct ehci_hcd		*ehci;
+	int			nports, index, n;
+	int			count = PAGE_SIZE;
+	char			*ptr = buf;
+
+	ehci = hcd_to_ehci(bus_to_hcd(class_get_devdata(class_dev)));
+	nports = HCS_N_PORTS(ehci->hcs_params);
+
+	for (index = 0; index < nports; ++index) {
+		if (test_bit(index, &ehci->companion_ports)) {
+			n = scnprintf(ptr, count, "%d\n", index + 1);
+			ptr += n;
+			count -= n;
+		}
+	}
+	return ptr - buf;
+}
+
+/*
+ * Dedicate or undedicate a port to the companion controller.
+ * Syntax is "[-]portnum", where a leading '-' sign means
+ * return control of the port to the EHCI controller.
+ */
+static ssize_t store_companion(struct class_device *class_dev,
+		const char *buf, size_t count)
+{
+	struct ehci_hcd		*ehci;
+	int			portnum, new_owner, try;
+	u32 __iomem		*status_reg;
+	u32			port_status;
+
+	ehci = hcd_to_ehci(bus_to_hcd(class_get_devdata(class_dev)));
+	new_owner = PORT_OWNER;		/* Owned by companion */
+	if (sscanf(buf, "%d", &portnum) != 1)
+		return -EINVAL;
+	if (portnum < 0) {
+		portnum = - portnum;
+		new_owner = 0;		/* Owned by EHCI */
+	}
+	if (portnum <= 0 || portnum > HCS_N_PORTS(ehci->hcs_params))
+		return -ENOENT;
+	status_reg = &ehci->regs->port_status[--portnum];
+	if (new_owner)
+		set_bit(portnum, &ehci->companion_ports);
+	else
+		clear_bit(portnum, &ehci->companion_ports);
+
+	/*
+	 * The controller won't set the OWNER bit if the port is
+	 * enabled, so this loop will sometimes require at least two
+	 * iterations: one to disable the port and one to set OWNER.
+	 */
+
+	for (try = 4; try > 0; --try) {
+		spin_lock_irq(&ehci->lock);
+		port_status = ehci_readl(ehci, status_reg);
+		if ((port_status & PORT_OWNER) == new_owner
+				|| (port_status & (PORT_OWNER | PORT_CONNECT))
+					== 0)
+			try = 0;
+		else {
+			port_status ^= PORT_OWNER;
+			port_status &= ~(PORT_PE | PORT_RWC_BITS);
+			ehci_writel(ehci, port_status, status_reg);
+		}
+		spin_unlock_irq(&ehci->lock);
+		if (try > 1)
+			msleep(5);
+	}
+	return count;
+}
+static CLASS_DEVICE_ATTR(companion, 0644, show_companion, store_companion);
+
+static inline void create_companion_file(struct ehci_hcd *ehci)
+{
+	int	i;
+
+	/* with integrated TT there is no companion! */
+	if (!ehci_is_TDI(ehci))
+		i = class_device_create_file(ehci_to_hcd(ehci)->self.class_dev,
+				&class_device_attr_companion);
+}
+
+static inline void remove_companion_file(struct ehci_hcd *ehci)
+{
+	/* with integrated TT there is no companion! */
+	if (!ehci_is_TDI(ehci))
+		class_device_remove_file(ehci_to_hcd(ehci)->self.class_dev,
+				&class_device_attr_companion);
+}
+
+
 /*-------------------------------------------------------------------------*/
 
 static int check_reset_complete (
@@ -504,6 +601,16 @@ static int ehci_hub_control (
 					ehci_readl(ehci, status_reg));
 		}
 
+		/* transfer dedicated ports to the companion hc */
+		if ((temp & PORT_CONNECT) &&
+				test_bit(wIndex, &ehci->companion_ports)) {
+			temp &= ~PORT_RWC_BITS;
+			temp |= PORT_OWNER;
+			ehci_writel(ehci, temp, status_reg);
+			ehci_dbg(ehci, "port %d --> companion\n", wIndex + 1);
+			temp = ehci_readl(ehci, status_reg);
+		}
+
 		/*
 		 * Even if OWNER is set, there's no harm letting khubd
 		 * see the wPortStatus values (they should all be 0 except

drivers/usb/host/ehci.h

@@ -74,7 +74,11 @@ struct ehci_hcd {			/* one per controller */
 
 	/* per root hub port */
 	unsigned long		reset_done [EHCI_MAX_ROOT_PORTS];
-	unsigned long		bus_suspended;
+	/* bit vectors (one bit per port) */
+	unsigned long		bus_suspended;		/* which ports were
+			already suspended at the start of a bus suspend */
+	unsigned long		companion_ports;	/* which ports are
+			dedicated to the companion controller */
 
 	/* per-HC memory pools (could be per-bus, but ...) */
 	struct dma_pool		*qh_pool;	/* qh per active urb */